Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$208.64	12.699%	$235.1352	$235.14	$235.15	$235.10
Purchase #2	$18.81	3.228%	$19.4172	$19.42	$19.40	$19.40
Purchase #3	$196.97	13.562%	$223.6831	$223.68	$223.70	$223.70
Purchase #4	$183.83	4.449%	$192.0086	$192.01	$192.00	$192.00
Purchase #5	$151.95	13.791%	$172.9054	$172.91	$172.90	$172.90
Purchase #6	$247.88	12.484%	$278.8253	$278.83	$278.85	$278.80
Purchase #7	$35.81	7.537%	$38.509	$38.51	$38.50	$38.50
7 purchase totals =	$1,043.89		$1,160.4838	$1,160.50	$1,160.50	$1,160.40